1. Field of the Present Invention
The present invention relates to a load drive controller adapted to prevent a drive transistor for driving a load from overheating, and to a load drive control system having a control means.
2. Description of the Related Art
A control unit having a temperature protection function of preventing a drive transistor for driving a load from overheating has hitherto been proposed in, for example, JP-A-2005-217399. Specifically, a control unit is proposed which includes a circuit substrate with an electric circuit formed thereon, a drive transistor installed on the circuit substrate for driving a load, a cutoff member for electrically connecting the drive transistor with the electric circuit separated from the drive transistor, and an operation member adapted to be inductively activated when the drive transistor overheats.
In such a control unit, the operation member is actuated when the temperature on the drive transistor exceeds a high temperature that is unacceptable. That is, when the operation member is pressed against the cutoff member, the cutoff member is then moved to be separated from the circuit substrate, so that the drive transistor and the electric circuit are electrically disconnected. In this way, the current passing through the drive transistor is stopped, thereby protecting the drive transistor from heat.
Although the above-described known technique can protect the drive transistor from overheating, the current passing through the drive transistor is completely stopped, thereby leading to shutdown of the control unit itself. In other words, this leads to termination of the function of the entire system using the control unit, thereby affecting users using the system employing the control unit.